Our present invention relates to a stack of multiple plastic foil bags and to a method of making that stack. More particularly, the invention relates to bags of the type which are used with automatic packaging machines and in bags which are individually pulled from the stack and separate along perforation lines from a bag residue which remains as part of the stack.
In the continuous production of bags it is generally known to collect the bags which are made together to form stacks or pads each with a predetermined number of bags. The collection device can be, for example, a pin-type stacking conveyor with a horizontally-moving conveyor chain carrying pins on which the individual bags are stacked. Openings are stamped or punched into the bag at distances corresponding to the spacing of a pair of stacking pins and the bags are placed over those pins by threading the pins through the openings.
It is also known to hold bags of a stack together by means of a wire bracket which has its shanks traversing the openings formed in a flap part of the bag. For this purpose the bag stack can be lifted from the stacking pins of the pin-type stacking conveyor and placed over the shanks of the wire bracket or the shanks of the wire bracket can be inserted through the holes in the stacked bags to allow the wire bracket to be used to remove the stacks from the pins.
The ends of the wire bracket can bear upon front and rear cover sheets which are provided between the bracket ends and the plastic bags and the stack can be secured by safety plates or rubber plugs fitted onto the shanks of the wire brackets. The steps involved are usually performed manually by an operator.
Mention should be made of the fact that such bags are generally provided with unilateral flaps and the suspension holes are customarily provided in those flaps. The term xe2x80x9cunilaterallyxe2x80x9d is used to indicate that the flap is generally an extension or provided as a separate part of one of the broad walls of the bag, the other broad wall terminating at an edge which can be pulled away from the first-mentioned broad wall to form the filling opening of the bag. The bag stacks hitherto provided are expensive because of the need for auxiliary materials, like the wire stirrup and the front and rear cover sheets or the plates or plugs. Furthermore, the bag stacks themselves are difficult to package and transport largely because of the presence of the wire stirrup. When product is to be introduced into the bag in an automatic-packaging machine, the flap part is usually turned off along the bag opening and can result in a sloppy appearance of the bag since the front edge is no longer smooth. In some cases, moreover, the wire bracket or stirrup must be returned to the manufacturer for recycling.
It is also known, in the production of bag stacks, to interlock the bags by pressing one of the bags into the other at interlocking points at the corners, usually of flaps of the type described. The interlocking approach simplifies the packaging of the bags and makes the separation of the bags from the stack somewhat neater and frequently simplifies bag production. There is no need for the brackets and stirrups and thus the manufacturing and handling of the stacks can be more cost-effective, especially since the cost of the wire brackets and of their return to the manufacturer of the bags is eliminated.
Nevertheless the production of stacks of bags is capable of improvement.
It is the principal object of the present invention to provide an improved bag stack which ensures a more aesthetic appearance of the bags after separation from the stack and more economical fabrication of the stack than has been the case hitherto.
Another object of the invention is to provide an improved method of making a bag stack, particularly for use in the machine packaging of goods.
Still another object of the invention is to provide a method of stacking plastic bags of film or foil whereby drawbacks of earlier bag stacks are avoided and, in addition, to provide an improved bag stack with the advantages gained by that method.
These objects and others which will become apparent hereinafter are attained, in accordance with the invention in a bag stack formed from bags having a unilateral flap which is provided in corner regions with separating lines of perforations and within the corner region, the means for retaining the bags in a stack, e.g. the hole along the margins of which the bags of the stack can be held together.
According to the invention, within the corner region bounded by the perforations and thus within the tear-off segments of the flap, a means for incorporating the bags in the stack can be provided, for example, in the form of cross-shaped or star-shaped seal arrangements.
According to the invention, the bag flap is placed over a stack of pins of the collection device so that the collection is hugged by the lobes separated by the cross-shaped or star-shaped array of slits and, once the stack is formed on these pins, the bags of the stack are held together, also within the corner region delimited by the perforations.
The star-shaped or cruciform array of slits, referred to here as the means for stack incorporation, are arranged in corner areas of the flap delimited by the perforations and thus in a pair of segments which remain behind when the remainder of the flap is separated from the corner segments but stack-incorporation means of this type has precisely defined contours which snugly grip the stacking pins by the lobes which are spread apart as the stacking corporation means are forced over the pins. The result is an optimal suspension of the individual bags on the pin and support for the bags as they are padded together.
Another advantage of the provision of the slit arrays within the corner areas delimited by the perforations and of providing the actual attachments of the bags together in these areas, is that the bag can be separated from the two corner segments which remain on the stack significantly more neatly than has been the case.
Furthermore, the system of the invention provides a central area of the flap between the perforations which is free from discontinuities, holes, slits and the like and which can be used to receive print, for labeling or the like, without disturbance resulting from such discontinuities.